A human lung carcinoma cosmid library has been constructed and a series of clones corresponding to the complete human c-fes and c-abl genes identified, subcloned in appropriate plasmid vectors, and subjected to detailed restriction endonuclease analysis. Neither gene exhibits detectable transforming activity even when linked to SV40 promoter sequences. The avian v-fps gene was found to map at the same position in the position in the human genome as the mammalian c-fes gene and the chromosomal location of each of these genes has been determined. Tyrosine phosphorylation acceptor sites within v-fes and v-abl have been localized with respect to trypsin cleavage sites. High level production of transforming growth factor was found in v-abl- and v-fes transformed cells. These factors have been purified to homogeneity and subjected to partial amino acid sequence analysis. Monoclonal antibodies with specificity for various domains of gag-fes- and gag-fms-encoded polyproteins have been isolated. A major 90,000 Mr polyprotein gene product of a new transforming retrovirus isolate, 3611-MSV, has been identified and shown to lack protein kinase activity.